PURPOSE: To improve the leading edge characteristic of an output waveform, by connecting the collector of a non-saturation transistor in an open collector type of output circuit, to the output terminal of an output transistor, and the emitter, to the base of the output transistor.

CONSTITUTION: A transistor 7 is a transistor to shallow the saturation of an output transistor 1, and by means of an operation in a reverse direction, the base current unnecessary for a drive out of the base current of the output transistor 1, is permitted to flow to the collector of the output transistor 1. Consequently, the saturation of the output transistor 1 is shallowed by the non-saturation transistor 7, and a charge accumulated at the base is reduced. Therefore, a time to discharge the charge to the ground 3 through a resistance 2 is shortened, thereby, the rise of the output waveform is accelerated.